Since the launch of the Earth Resources Technological Satellite (ERTS) in 1972, satellite imagery-based information acquisition, dissemination and exploitation (e.g., for natural resources monitoring and assessment) has reached a billion dollar industry. The importance of spatial data handling (as opposed to conventional aspatial statistical analysis) was recognized in the early 1970s, but commercial applications of this field were not realized until the early 1980s, when lower-cost microcomputer technology was accepted as a platform for spatial data analysis.
The field of spatial data handling is known today as Geographical Information System (GIS), and includes "an organized collection of computer hardware, software, geographical data and personnel designed to efficiently capture, store, update, manipulate, analyze, and display all forms of geographically referenced information" (ESRI: Understanding GIS: The ARC/INFO Method, 1992).
Images could be combined and/or analyzed to a certain degree, as could map data. But heretofore, no successful process for combining image and map data and analyzing same has been implemented.
The potential benefit from combining image and map data into one integrated information system was recognized as early as the mid-1980s, but integration of image analysis and GIS has been limited essentially to visual overlay analysis. Commercially-available GIS systems do not provide an effective and efficient mechanism for a total, seamless integration between image and map data.
This artificial separation is largely due to historical factors and partly due to the inherent dissimilarity between image and map data, as hereinbelow described. Historically, cartographers used point, line and area symbols to generate a map. Traditionally, map data were stored in a vector format as points, lines or polygons. In contrast, image processing and remote sensing researchers treated image data as a set of matrices. Therefore, by default, image data were and continue to be coded in a raster format.
This dichotomy between vector and raster data format is reinforced by the inherent characteristics of images vs. maps. The building block of image-based information is a pixel, whereas that of a map is a polygon. (A point or a line is a special case of a polygon.)
Spatial relationship analysis between two or more layers of images is exceptionally difficult to perform. A buffer zone (a zone generated within a given distance of a specified set of coverage features) might be used to combine two or more overlaid images (sewer lines and streams, for example), using conventional image processing methods. This is called "vertical integration". But how could an imaging processing system be used to indicate that a feature such as brushland from a first band is located "within" a buffer zone created by a stream system in a second band? The term "horizontal integration" is used to describe the traversal of spatial locations on one plane. It can be seen, therefore, that the field of image analysis lends itself to principles not only of data processing, but of fuzzy logic and expert systems.
Conventional image processing is not designed to handle spatial relationships. Fundamentally, words such as "within", "surrounding", "touches", "left of", "near", etc. cannot be used or understood. This is unfortunate, because even if an expert system were created to handle spatial and aspatial data efficiently, the need for a complex programming language would tend to defeat an obvious goal: simplicity of use. Researchers would find a powerful analysis tool to be unmanageable due to its operative complexity.
It would be advantageous to allow GIS, image processing, and remote sensing users to improve their capability in object extraction, change detection and map information updating.
It would also be advantageous to provide a mechanism for using a variety of data sources for a common geographical region.
It would also be advantageous to provide a system for facilitating simultaneous spatial and aspatial information fusion and analysis.
It would also be advantageous to provide an expert system (interactive or automated), including a rule set, capable of understanding English-language statements.
It would also be advantageous to provide a system for performing vertical and horizontal information integration simultaneously.
It would also be advantageous to reduce the cost of GIS usage through an efficient and effective information integration between imagery and map data.